Control valve adapted for pressure differential servomotor use



Feb. 2l, 1961 G. T. RANDOL 2,972,339

coNTRoL vALvE ADARTED FoR PRESSURE DIFFERENTIAL sERvoMoToR USE original Filed July 8, 1955 2 Sheets-Sheet 1 Sv Sx Feb. Z1, 1961 G. T. RANDoL CONTROL vALvE ADARTED RoR PRESSURE DIFFERENTIAL SERVOMOTOR USE Original Filed July 8, 1953 2 sheets-sheet 2 United States CONTROL VALVE ADAPTED FOR PRESSURE DIFFERENTIAL SERVMOTOR USE Glenn T. Randol, Mountain Lake Park, Md., assigner of fifty percent to Hamill-Markus Industries, lne., Warren, Mich.

4 Claims. (Cl. 121-465) The present invention relates to novel valve mechanism for controlling pneumatic devices, and more particularly to valve mechanism for controlling pressure differential operated servomotors adaptable for use in the brake or steering system ofl automotive vehicles and the like: T his application is a division of my copending application Serial No. 366,736, filed July 8, 1953, now matured as Patent 2,903,855, dated September 15, 1959.

In my copending application referred to above, I have disclosed a vacuum-operated booster brake mechanism including a iiuid pressure actuated servomotor which is controllable by a novel and improved valve mechanism through the medium of an operator-operated member exemplarily illustrated as a suspended-pedal pivo-tally supported at its upper end on a bracket attached to the lirewall of the motor vehicle in the drivers compartment. The controlvalve mechanism is characterized by certain novel features of construction and'operation which relate to the valve mechanism per se, thus rendering such valve mechanism applicable to the control of a wide range of pneumatically-actuated devices including its association with vehicular brake systems. These features of the valve mechanism per set form the subject-matter of the present application.

An object of the present invention is the provision of new and improved control valve mechanism operatively associated with the movable wall of Vsuch servomotors to control energization of the same, said valve mechanism including at least two principal cooperating elements relatively displaceable from a normal off position wherein -pressures are balanced on opposite sides of said wall to inactivate the same, and to an on operating position wherein differential pressures are established on opposite sides of said wall to activate said servomotor, and a normally preloaded spring reacting between a fixed member and the pedal operated valve element t produce progressively augmented reactive force on the pedal in accordance with the operating movement of the latter from normal position, and wherein said spring is effective in response to removal of operator force from said pedal, to urge the said Wall of its normally releasedl position and the two valve elements to their normal off positions.

In one of the disclosed embodiments of my novel control valve means there is provided two principal cooperating elements one of which is slidably intertted with atent O la Patented Feb. V21,1961

operably disposed between said member acted on by said reactive and return spring and the pedal, and a releasable connection of novel character is provided between the p-air of slidable elements enabling the outer of said pair of elements to have a floating action between the third and inner elements whereby thrust deflections induced by pedal actuation of the inner element bypass the outer element for longer service life with minimum wear between the two cooperating elements. p

A further object of my invention is to provide novel control valve means incorporating pre-energized reactive and return spring means which provide instant opposition to initial pedal movement to oppose operation of said pedal from normally released position, said spring means being additionally energizable to progressively augment resistance to pedal movement substantially proportional to the operating movement of said movable wall in a thrustproducing direction.

A further object of the present invention is to produce in thrust-applying means of the type referred to, novel pedal control of fluid pressure operated means whereby pedal movement is not limited to the actuating movement of the control valve mechanism operatively associated therewith, thus to provide a range of additional or supplemental movements of thepedal to that required for valve actuation thereby, for controlling such thrust-applying operations in cooperation with, or independently of the fluid pressure means without actuating the elements of the valve mechanism beyond their full thrust-applying position of control.

In the interest of brevity, other objectives features will be noted hereinafter in lieu of `presenting them categorically in the above general statement of the nature of the invention. A more comprehensive understanding of the advantages of the invention and its mode of operation may be had from the detailed description thereof to follow with reference t0 the drawings which the other, and which are operatively disposed between a l member acted on by said spring and the pedal whereby said member reacts on the wall, the valve elements, and the'pedal to reset theseparts to their normal inactive positions. In another disclosed embodiment, a modified valve mechanism is provided wherein there are three principal cooperating elements, a pair of which is telescopically-related and slidably interfitted within the third element, and capable of relative and conjoint movements with respect to eachother and to the third element. The

inner slidable element of said pair of elementsbeing ber disclosed herein ,as a piston rod or plunger 72' is accompany this specification. f

In the drawings: Y

Figure 1 is a longitudinal vertical section of my new and improved valve mechanism constructed in accordance with the present invention, and shownin operative association with a fluid pressure operated servomotor, wherein the parts are in their normally released disposition;

Figure 2 is a view similar to Figure 1 showingA an operated dispositionof the valve mechanismvcorresponding to an energized status of the associated servomotor;

Figure 3 is a fragmentary sectional view taken along the line 3-3 of Figure 2; Y y

Figure 4 'is a fragmentary longitudinal section illustrating a modified form of the invention;

Figure 5 is a fragmentary longitudinal section of another modied form of the invention; l

Figure 6 is a transverse sectional view taken along th line 6--6 of Figure 5; and i Figure 7 is a view similar to Figure 5, demonstrating an operatively adjusted disposition thereof.

Referring to the drawings: f Y K The illustrative embodiments of my new and improved control valve mechanism are disclosed in connection with a pressure differential operatedl booster servomotor adapted to operate in part the hydraulic master cylinder in a brake system on automotive vehicles and the like, said servomotor being designated asa whole 28 and is 'operatively associated with a hydraulic master cylinder designated as a whole-42 and having a cylinder 68 fitted witha movable piston or wall 70normally disposed in released position asv shown in Figure 1. The cylinder is divided interiorly by said wall into a constant (atmospheric) pressure chamber 91 and a variable pressure (vac- Y uum) power chamber 89. A pressure-transmitting memand salient y f these views, and which have been previously described, are identied by the same reference numerals distinguished, however, by the addition of the letter b to each. v

The modified air control valve element or piston is designated 164, and is slidable in the tubular lmember 122b between the abutment ring 140band a split stop ring 166 which is seated in an internallgroove provided therefor in said tubular member as shown. The normal or brake-released position of the valve piston 164v is exhibited in Figure 5, wherein it is seen that the right end of said element abuts the ring 140b, whereas a projecting annular flange 168 thereof is disposed in spaced relation to the right of the stop ring 166.

The piston-like member earlier referred to is designated 170, and is also slidably disposed in the tubular member 122b. It includes a socket segment 172 disposed contiguous to the free end of the plunger 96h, and a sleeve vsegment 174 disposed within and coextensive with the valve element 164. As shown in the drawings, the valve rod 144b has a ball and socket connection 146b with segment 172, and rightward movement of the member 170 is limited by the stop ring 166. The sleeve segment 174 which is smaller in diameter than the valve element 164, has formed therein circular openings 176 and an annular external groove 178 in which, as particularly demonstrated in Figure 6, is seated an expansive yieldable split ring or collar 180. The periphery of the collar 180 has formed thereon a series of parallel and closely generated V-shaped serrations 182 which cooperate with a series of complementally shaped internal grooves '184 provided in the valve element 164, thus to releasably interconnect the member `170 rand said valve element for limited movement together. .First and second annular external grooves (fluid chambers or channels) 186 and 188, respectively, are formed in spaced relation by an annular land 189 on the valve element 164, the groove (fluid channel) 18S communicating with the hollow interior of said valve element via radial ports 190.

The first external groove (fluid channel) 186 is in fluid communication with the vacuum source (not shown) in the identical fashion described relative to the groove 126 of the Figure 1 embodiment of the valve element. The second external groove (iluid channel) 188 normally vents the servomotor vacuum chamber 89h to atmosphere via ports 88b, annular chamber 90b, port 138b, ports 190, ports 176, atmospheric chamber 91 and conduit 38 as illustrated in Figure l.

It is noted that one ofthe features inherent in the Figures 5 through 7 construction, is that wear with respect to the air control valve element 164 is negligible, in that pedal forces are not applied thereto directly, as should be manifest but will be more fully explained hereinafter. Another feature is provided by the ratcheting conection 180, 182, 184 which functions to ,accommodate relative displacement of the actuatable member 170 with respect to the valve element 164 upon the latter being established in either open or closed position of control under influence of limited simultaneous movement with said member 170 provided by said ratcheting connection, and thereby, enabling operation of the valve element to such positions of control to be. advanced with respect to the normal position from which the actuatable member is effective to control said valve element, said advancement being limited to the relative number of cooperating teeth on the collar 180 and the valve element respectively.

Operation The main embodiment of the invention is exhibited in Figures 1 through 3, and the operation thereof will now be explained with reference alsoto Figure l. The normal, that is the off condition of the valve mechanism is depicted in Figure l, wherein the disposition of Vthe pedal member 48 is fully retracted or released. The `operative, that is the operating on position ofthe valve 75 POS'ed t0 the rlght 0f the PON 138- m'echanismis depicted in Figure 2, wherein thev disposition of the pedal member 48 corresponds to a depressed status thereof to effect relative adjustment of the parts as shown in Figure 2.

In the o status of the valve mechanism, the conical compression reactive and return spring 106 biases the piston and consequently its associated rod 72 to the positions thereof portrayed in Figure l. As a result, the annular element 76 tilts the stem 66 of valve assembly 64 whereby the hydraulic chamber of cylinder 54 is placed in fluid communication with reservoir 60. As a further result, plunger 96 maintains the air control valve piston 124 against the abutment ring 140 whereby to place the pedal 48 in actuatable status, and to simultaneously provide a non-communicative relationship between the power cylinder chamber 89' and the source of vacuum, such as, for example, the engine-intake manifold, as should be apparent from the preceding description augmented by an inspection of Figure 1.

The lost-motion'connection 98, 100 which defines the relative operating movement of the valve element 124, with the brakes released as portrayed in Figure l, is fully established between the radial pins 98 and forward ends of the longitudinal slots 100 in the plunger 72 with the opposite sides of the pins in engagement with the confronting circular end of the piston boss 86. The inner marginal surface of the sleeve segment 112 engages the confronting sides of the pins under influence of the re'- active spring 106 whereby the pins are normally impinged between said sleeve segment and boss 86, best demonstrated in Figure l, in readiness for pedal actuationr to controla brake-applying operation of the'hydraulic'cylinder 54 assisted by the servomotor 50 as is understood. During relative movements of the spring vseat 104 laccommodated by the lost-motion connection aforesaid, the plunger and valve elements 96, 124 respectively are moved simultaneously therewith by the pedal 48 via interconnecting link 144 to dispose valve land to the left of port 138 to open the latter (see Figure 2) thereby energizing the power piston assembly 70, the degree of energization being determined by the extent to which the port 138 `is exposed to the annular vacuum channel 126. At full open position of the valve element 124, the radial pins 98 are brought into engagement with the forward ends of the slots 100 wherein the lost-motion therebetween is full taken up enabling pedal-actuation by the operator to be applied via said pins to operate the plunger 72 to apply yand release the brakes supplementarily to power assistance provided by corresponding to any given valve open position until the lost-motion is taken up for direct foot operation of the hydraulic cylinder 54 as explained above. Accordingly,

kthis novel arrangement of spring control in a brake-applying direction provides maximum utilization of the 'pressure ldifferential acting across the piston 70 to assist in applying the brakes since the biasing effect of the return spring 106 is rendered inactive on the piston during power assistance operations thereof, but during release of the pedal i 48, this novel spring arrangement becomes effective on the piston 70 via the pins 98 engaging the boss -86 to return the power assembly to released position portrayed in Figure 1 and at the same time provide the operator with a sense of the degree of release, and return the valve element 124 to its normally closed position, best illustrated in Figure'l wherein ther valve land12i5l is dis- It should also be noted that the biasing action of spring 106 supports the weight of the pedal and its associated link 144 in the fully released position of said pedal, said spring preferably having been installed the power cylinder in pre-stressed condition to provide instant resistance to initial pedal movement. ln consequence of this arrangement, reaction or driver feel is always in evidence at the touch of the pedal, irrespective of the degree of pedal depression. Manifestly, whenever the pedal is incrementally depressed during a brake-applying operation, reactive evidence becomes increasingly pronounced inasmuch as the spring 1% becomes increasingly stressed, as the piston 7? advances leftward to apply the brakes. In other words, initial reaction is instantaneous (there being no lost-motion movement of the pedal as found in prior art arrangments); and further, the reaction is constantly and increasingly effective throughout the full operating stroke of the pedal. Thus, smooth braking control is provided throughout the range of pedal movements from the fully released to the fully depressed positions thereof.

It is also noted that the vacuum-power cylinder chambers 89, 91 are in communication with the atmosphere to balance pressures on both sides of the piston 70, via conduitrSS, air control valve element 124 and the circular openings 136 therein, chamber 9i), and ports 88.

Assuming now, that with the vehicle engine in operation, it is desired to apply the brakes, the pedal 48 will be actuated by the drivers foot in the ordinary manner.

Initial depression of the pedal causes the air control valve element 12d to move leftward relatively to the piston 70 until the annular land 135 thereon cornes into registry with the port 13S. As a result, communication between atmosphere and the vacuum chamber 8g is interrupted momentarily, while at the same time, plunger 96, which obviously moves leftward also a corresponding distance, further compresses the spring 106 slightly without disturbing the stationary aspect of the piston 7d and its rod 72. This is so because the radial lugs 9S areV free to move leftward in the slots 10b independently of the piston and rod, and are in engagement with the flat segment 114 of the cup-shaped spring seat 104. The radial port 102, as previously pointed out, prevents any pressure buildup in the axial bore 92 as the plunger progresses.

Assuming now that the pedal is further depressed slightly, the valve element 124 and the plunger 96 also advance therewith, whereby Kto uncover the port 138 yand to additionally compress the spring 106. Simultaneously with the uncovering of the port 13S however, vacuum chamber 89 is placed in iluid communication with vacuurn via ports 83, chamber 90, port 138, annular groove 126, passage 13d, flexible connection 132, and vacuum conduit 1S. AAs a result, the piston 70 and its rod 72 immediately move to the left because of the pressure differential effective across opposite sides of the piston 7&9 as is understood. lnitial movement of the piston rod eitects disengagement of its disc 76 from the depending stem 66 oi the valve assembly 6d, whereby said assembly automatically seals the opening o2 to prevent communication between the hydraulic chamber of cylinder 54 and reservoir ed. Beginning at this point in the operation of a brake application, and upon further depression of pedal 48, the piston 7i?, its rod 72, the valve ele- `ment 124i, and the valve rod 144 advance as a unit with said pedal, whereby to cause hydraulic pressure to be increasingly applied via angular passage 5S, residual check valve 56 and piping il to the brake cylinders (not shown), in consequence of volumetric displacement of duid-under pressure from the hydraulic chamber aforesaid.

Manifestly, as the unit referred to advances incrementally to the brake-applied position thereof illustrated in Figure 2, the inherent and thus further compressed expansive force of the return spring 106 transmits to the drivers foot successive reactions corresponding in intensity to the distance the pedal 4S has moved 'in such brake-applying direction. Y

Thus it should be evident that my invention provides novel and improved pedally-controlled power brake mechanism, wherein` initial depression of the pedal 48 actuates the valve piston 124 to iirst isolate the vacuum chamber 89 from atmosphere, to thereupon evacuate said chamber and concurrently seal off fluid communication between the chamber of hydraulic cylinder 54 and reset* voir 60 as the piston 70 and its rod 72 are caused to advance in consequence of atmospheric pressure in chamber 91 acting across the piston 70, and to thereafter by a combination of evacuation, atmospheric pressure, and pedal depres-sion, to increase or decrease the hydraulic pressure of brake application as desired or required.

At the same time it should be apparent that the invention provides for the operator by way of the spring 106, an ever-present and automatically discernible feel Y of the brake situation, irrespective of the extent of pedal depression.

The operational behavior of the reactive and return spring 106 referred to above is unique in that it produces control characteristics in the way of reaction against which the control valve piston 124 is adjusted to control operative energization of the vacuum-motor 50. This reaction increases above normally preloaded status of this spring in direct proportion to the distance .the pedal 43 is depressed, and therefore, such spring resistance alone would not necessarily have a magnitude correlated with the amount of thrust or braking force in eifect at every position of the pedal, and too, pedal-load would increase toward the end of the full operating stroke of the plunger 72 actuated by the vacuum-motor to an undesirable degree which would defeat-the objective of reduced pedal effort.

As this spring is additionally compressed above its normally preloaded status, it provides increasing re sistance in relation to pedal movement up to the point the plunger encounters substantial resistance, and thereafter, resistance becomes substantially constant on the pedal y48 as a consequence of the substantially stationary condition of the thrust-inducing parts acting on the load or non-compressible column of brake fluid in the present application of the invention as is understood. I Since the iluid becomes pressurized at diiferent stations along the full operating stroke of the motor-actuated thrust-member or plunger 72 due to wear on the brake linings and parts, and to leakage of the various seals in the hydraulic braking system, it will be appreciated that if the pressur1zed state of the fluid to apply the brakes becomes eiective toward the end of the full operating stroke of the plunger 72, that the reaction from the lspring 106 can become severe resulting in a moderately hard-pedal due to rapid buildup in the force of this spring from its normally preloaded status, the latter providing the operator with accurate sensing to initially apply the brakes thus preventing sudden braking applications which would possibly result in a power-surge if the operator lacks this awareness as he applies the brakes.

Reduction -of .this spring reaction principle to commercial usage, has demonstrated that the preloaded weight in braking opplications should be set at approximately 20# and rated to react at 60# at the end of the full operating stroke of the plunger 72, which force when transmitted through the pedal leverage ratio reacts on the operators foot at 5 to 15u'- through the full operating stroke of the plunger where a normal height pedal is employed; but if the pedal ratio is lowered to accommodate use of a low-pedal with less mechanical advantage, reaction from this spring increases progressively to a limited extent that converts the low-pedal into a moderately hard-pedal as aforesaid through the stage of operating the control valve piston 124 from normal ofi position to operating on position to control operation of the vacuum-motor 56. Accordingly, this spring sary physical perception of the work or braking force in effect.

With attention directed to Figure 2, it is noted that the invention provides safeguard means in the event of partial or entire power failure. It will be remembered that the disposition of the mechanism exhibited in Figure 3 presents the normal brakes-fully-applied status, wherein the vehicleis at a standstill, or should be as is understood. However, should it perchange happen that the vacuum-power force per se would fail to arrest forward travel of the vehicle completely, a slight additional pedal depression is provided for, in that in consequence thereof, the radial lugs 9S may be brought to bear against the end walls of slots 100, whereby the piston 70 and its rod 72 can be advanced directly and solely by driver foot application, resulting in increased hydraulic pressure delivered to the brake cylinders.

From the foregoing, it should be clearly apparent that this invention is admirably suited for incorporation in booster motors particularly suited to control brake systems on trucks, busses, and like vehicles. wise be apparent how intermittent full brake application and partial release operations may be attained and 1nstinctively controlled eifortlessly by pedal actuation on the part of the operator. It should further be apparent that the mechanism enables the operator to normally apply a brake-holding status to the systemV at any point within the range of pedal movements which may be had between the Figure 2 disposition of said mechanism, and the disposition thereof which obtains when the annular land 135 of control valve 124 is in registry with the port 138 responsive to halting the pedal.

It is of course to be understood that when said land is in registry with Vport 138 the latter is covered, inasmuch as the diameter of said port is of smaller extent than the width of land 135. Thus it should be evident that wheneverppedal depression ceases at any point in a brakeapplying operation, registration of said port and land ,automatically follows, in consequence of which action .the brakes are held on by the then existing substantiallyy counterbalancing forces acting on opposite sides of the piston7t). A h

The Figure 4 embodiment of the invention operates in substantially'the same manner as the main'ernbodirn'ent. In this construction, however, the spring 160 functions only in the usual and conventional sense of returning the piston 70 to brake-released position in response to .a closing of the air control valve. That is to say, s aid spring'lt) is a conventional conical compression spring which had been initially installed in cylinder 68 in a compressed condition. Consequently, this 'spring does.4

whatever in accordance not transmit any brake feel with the concepts ofV myV invention, as should now be understood.

In the Figure 4 construction, the pre-tensioned conical spring 106a, interposed about the piston rod 72 between the stationary spring seat S and the slidably mounted spring seat 156 is the element which cooperates with spring 160 to return the vacuum-actuated piston 70 to normally released position as'illustrated in Figure rl and also servesto transmit' tothe 'pedal `43,` the feelfof brake application substantially proportional to the stroke 70a in applying the brakes.v .They said reactive of pistonV l movable-in response to movements of spring 10601, plunger 96a and its radial lugs 98a',

It should likegevaarte 70a, 'is initially installed in the cylinder in a pre-compressed condition according to the degree of initial reactive force desired on the pedal 48, so that it operates inthe same manner as that described with respect to the reactive spring 106Aof the main embodiment. In other words, since spring 10611 is independent of the return spring and is pre-tensioned, its action is not alected by the concurrent forces exerted by said return spring so that selective reactive springs 106a may be utilized to gain the desired reaction without modifying the return spring 160. As previously noted, the longitudinal slots 100a are of greater length than those of the main embodiment, whereby to accommodate a slightly increased advance of the radial lugs 98a in additionally energizing the spring 106a in response to pedal depression.

It is noted with respect to the Figure 4 modification, that the pre-tensioned spring 106:1 andcooperating slidable spring seat 156 arrangement are suitable also for effective operation in conjunction with the described air control valve construction portrayed in Figures 5 through,7.

In the Said Figures 5 through 7 embodiment of this invention, the aforementioned novel air control valve element 164 exhibits a yieldably releasable ratchet-connection between it and the piston-like actuatable member 170, the latter having a ball and socket connection with the pedally movable valve rod 144b. The releasableconnection referred to comprises the split expansible ring 180 seated in an external annular groove 178 provided therefor in said valve eleriient, and having minute `V-shaped peripheral serrations 182 as previously described. These serrations or grooves are closely generated in parallel circular relationship, and engage in the corresponding internal grooves 184 of the valve element 164. It is noted as illustrated in Figure 5, that a series of normally non-engaged internal grooves 184 is provided to the left of the ring 180,v whereby to accommodate 'a slightly additional movement of the Vpiston member and the valve rod 144b relative to the valve element 164 after the pedal 4S has been depressed suf- Aticiently to bring the annular ange'168 offsaid valve element into engagement with the stop' ring 166. In theV case where the actuatable member 170 has been relativelydisplaced with respect to the open position of the valve element 164 in the manner just described in response to pedal depression, release of thepedal would be immediatelyeffective through theratchet connection p in unison therewith. Accordingly, it is seen that the ratchet connection accommodates relative displacement of the I pedal and connected actuatable member 170 in a depressing or releasing direction 'of movement after firstY establishing the valve `element 164 inits selected position of control in unison with vsuch pedal movement.

An exemplication of a relative disposition of the mechanism corresponding to that just ldescribed is exhibited in Figure 7. There it is seen that the air control valve'element-164 has been advanced from the Figure 5 disposition thereof, by pedal depression to a position wherein the annular flange 168 abuts the stop ring 166. Up to that point, said valve element and the pistonmember 170 has moved in unison because of the releasable connection described, and the compression spring 106]; had been further compressed whereby to transmit brake application feel to the driver via plunger 96h, piston member 170, balland socketconnection 146b, valve rod -144b, and pedal 48. With left movementv of the valve relative to the piston Velement arrested, additionalpedal depression causes the resilient expansible ring .118,0 to contract and thus 'ratchet I over .the internal serrations'.184, whereby the piston member 170 advances independently of the valve element while retraction of the piston member responsive to pedal release, effects simultaneous movement of the valve element to closed position followed by restoration of the relative positions of the member 170 andvalve element as exhibited in Figure wherein pedal '48 is in normal fully released position. In consequence of this arrangement, it should be manifest that brake application directly from the pedal may also be had via the plunger element 961:, its radial lugs b, and the longitudinal slots while the valve element 16dis actuatable in unison with the pedal to open and closed positions at any point along full pedal stroke to enable on and off operations of the brakes despite relative operation aforesaid of the pedal with respect to the valve element is accommodated following such opening and closure thereof.

Although the illustrated and described releasable connection is preferable, it is noted that a split and therefore resiliently expansible ring having a smooth peripheral surface may be substituted for the serrated ring 180, and that a non-serrated internal bore may be provided in the valve element 16d. In such an arrangement, the frictional coeiiicient obtaining between the expansible ring and the smooth bore of the valve element would provide the connection between said element and the piston member 170.

Operational summary From the foregoing description, taken in conjunction with the various illustrations of the different embodiments of my invention, it will be seen that certain interrelated components of the valve mechanism possess similar functional characteristics such that interchangeability is readily effected, particularly in connection with the reactive spring controlling features and type of pressuretransmitting member 72 employed in the hydraulic cylinder 54, the latter may take the form of a piston having the `same cross-sectional area as the pressure chamber, or a plunger of less cross-sectional area than the chamber 54 which, in the latter case., would eliminate machining the interior of the pressure cylinder with a longer working stroke required of theV plunger. For example, the movable wall 7b may be either a piston or a flexible diaphragm connected to the pressure-transmitting member 72 with the adjacent end slotted at 169 with open ends and fitted with the bushing 94. This arrangement facilitates assembly of the cylindrical element 96 with the radial pins 98 installed integrally thereon or detachable. Where the pins 9S are inserted after the cylindrical element 96 has been placed in the position of Figure l, then the bushing 94 could be dispensed with, and the slots 100 formed in the wall of the plunger 72 .with closed ends, and while the cylindrical element 96 has been illustrated separate from the valve element 124 to avoid the need for accurate axial alignment therebetween, these two elements may be formed integrally as the disclosure clearly depicts.

Further considering the novel advantages provided by the reactive and return spring means 104, 106, this novel spring control enables rating of this spring to whatever degree of reaction desired since its action never interferes with the movement of the power .assembly 76.( vThis spring is continuously etfective on the brakepedal 45 via the spring seat 104, radial pins 9, cylindrical elementx96, valve element Md and link .-144 so that immediate yieldable resistance to movement of the pedal is encountered by the operator with' the inauguration ofV a brake applying depression of the pedal.- In this manner, the operator senses the degree of braking force being applied from the. instant pressure is applied on the pedal as the spring 1% progressively builds up in reactive force substantially proportional to the operating movement of the power-actuated plunger '72. Since the spring seat. 104 must move ahead-of the piston boss 86 for control valve actuation to induce the power piston 70 to be, energized, the force'exerted by spring v1% is rendered non-eiective against the piston thus providing maximum effectiveness of the power phase with a resultant higher point at which power-run-out would become effective than would otherwise occur, the latter condition representing maxi*- rnllm power application of the brakes and should an even greater braking force be required for the given stopping or slowing operation of the vehicle, then the operator Imust apply such additional pressure to the pedal 48 via the pins 98 engaging the ends of the slots 1% to bring the total brake applying force to the degree required.

it is also important to note that the auxiliary spring 166 of Figure 4 may be incorporated in either of the embodiments Figures l-3 or Figures 5-7 where a continuous biasing action is desired on the power-piston assembly 7i), 7Gb to supplement the reaction of the reactive springs 106 or 106b respectively during release of the brakes as is understood. This arrangement would find a practical application in installations of the present invention on heavy-duty vehicles and the like.

An important feature of braking control results from the use of a normally pre-energized spring, such as spring 106 or 106:1 reacting on the pedal 48 to provide instant resistance to movement of the pedal, such that in the event the brakes are applied initially by a sudden thrust of the pedal, this spring gives the operator an awareness of pressure being applied so that the power-boost application may be brought in to assist the pedal operation without abrupt shock and grabbing. This smooth mergence of the power phase with the pedal operation after the latter has inaugurated pressure build-up in the spring, avoids the possibility of power-boost lock of the vehicle whe-els with resultant tendency of throwing the `car occupants forwardly out of their seats, and sometimes leads to personal injury, loss of control or a potentially dangerous skid. Thus, the present invention inherently provides full control, predictableV response for complete braking safety without requiring special manipulation of the control pedal.

The present servomotor booster Sil is especially adapted for the replacement market since any conventional master cylinder assembly mounted in the engine compartment on the vehicleV firewall and which utilize for its operation a pivotally suspended pedal, may be used intact thereby appreciably lowering the cost to the car owner and greatly simplifying the installation where the unit is applied on after market cars. This noteworthy feature is provided by the use of the novel reactive spring means 104, 106 incorporated in the servomotor itself. Thus, the present liquid pressure producing device actually comprises two separate units; namely, the servomotor operably combined with the factory-installed hydraulic master cylinder adapted for conventional foot operation as is understood. This novel application of servomotor boost to a conventional master cylinder retains all of the brake control features provided by the latter with substantial reduction in operator effort. Where the present invention is merchandised as an accessory or after-market installation, only the servomotor is required since the master cylinder, pedal and linkage assembly, anddust boot factory installed on the car are utilized without alteration at a great savings to the car owner to provide power assistance in operating the brakes with no more after-installation maintenance being required than normally expected with a conventional footoperated system.

As the present disclosure clearly demonstrates, the servomotor Sil is the self-contained type in that it includes the reactive means on the operator control. This novel construction not only facilitates its installation in a motor vehicle, for example, but also utilizes the standard master cylinder without disassembly'thereof to form a unitary power-assisted braking control where incorporated in a hydraulic system. Vin the case of mechanical brakes, then the servo motor actuated member 72 would be mechanically linked to the brake actuating cam'with'l the reactive means 104, 106 serving to give the operator an awareness of the degree of braking force being applied by the servomotor for smooth braking applications. Y v

, Accordingly, the present invention provides .a yieldable force, such as the illustrated springs 106 or 106a, to constantly oppose the operator during operation of the vehicle brake system. This opposing force progressively builds up against the operator from a normally preloaded status, in substantially proportional relationship to the effective operating stroke of the movable wall 70. This is true, since the reactive force exerted by the spring increases as the pressure-transmitting member 72 is driven farther into the hydraulic chamber 54, thus giving the operator a feel or reaction from the instant he moves the pedal 48 to enable him to smoothly bring in the power phase with followup control to provide the degree of power-assistance desired until full power has been utilized if required.

The control valve 124 or 164 has the usual follow-up action, each of said valves being characterized by relative sliding movement with respect to its cooperating sleeve movable in unison with the power-piston assembly 70. As the power piston moves on its pressure stroke, it tends to overtake, and lap the control valve element, unless brake-applying movement of the pedal 48 continues. Whenever, the operator removes his force from the pedal, the control valve follows` pedalrmovement relative to the power-piston assembly 70 into the position shown in Figure l wherein the power chamber 89 communicates with the atmosphere, by reason of the force exerted by the reactive spring 106 on the valve member 124, said spring also simultaneously-acts on the power-piston 70, with the valve member aforesaid in the position noted, to return it to released position depicted in Figure 1.

If the operator desires to add physical force after the full force (power-run-out) of the servomotor 50 has been developed, or, if there is power failure, direct physical force on the plunger 72 can be exerted via the valve element 124, plunger 96, radial pins 98 engaging the forward ends of the slots 100. f

From the foregoing description augmented by an inspection of the drawings, it should be manifest that my invention provides novel valve mechanism vadapted to achieve its objectives in a highly efficient manner.

Although I have illustrated and described preferred em.- bodiments of my invention, I do not wish to limit such to the exact construction or arrangement of parts shown, since it is evident that modifications and substitutions may be made therein without departing from thewproper scope or fair meaning of the subjoined claims.

Having thus described my invention I claim:

1. In a control valve for use in cooperation with ay power member movable under inuence of a pressure differential, the improvement which comprises. a housing having a cylindrical wall encircling a longitudinal bore; a piston-type valve element slidable in said longitudinal bore from a normal position; a first port through said wall communicating with said longitudinal bore; two longitudinally spaced annular lands on the valve relement defining a pair of annular fluid chambers, one of said chambers continuously communicating with the first port; an atmospheric passage leading to said other charnber; a second port through said wall controlled by one of said annular lands to selectively connect said uid chambers to said fiuid passage and said second port, and to said latter port alone, respectively; a stop element incorporated between said wally and one end of said valve element to establish the normal position of the latter; a stationary member; a slidable member having a normal position; an element interconnecting said valve element with said slidable member for conjoint movement; and a normally preloaded spring reacting between saidstationary member and the slidable member to bias the latter member and said valve element to their respective normal t. f 14 positions aforesaid wherein said second port is in munication with said fluid passage.

2. In a control valve for use in cooperation with a power member movable under influence of Ia pressure differential, the improvement which comprises: a housing having a cylindrical wall defining a longitudinal bore; a tubular valve element slidable in said bore from a normal position; a first port through said wall communieating with said bore; two longitudinally spaced annular lands on the valve element defining with said bore a pair of annular fluid chambers, one of said chambers continuously communicating with the first port; an axial bore through the valve element; a port through that portion of the valve element in circular alignment with said other chamber continuously communicating with said axial bore; a second port through said wall controlled by one of said annular lands to selectively connect the two chambers aforesaid to said second port; a fluid passage leading from said other chamber to atmosphere; an actuatable member telescopically-related to said valve element to have sliding movement in said axial bore from normal position; an annular external flange defining one end of the actuatable member and normally engaging the confronting end of said valve element; a series of closely generated circular toothed elements disposed in parallel yrelation in a portion of the cylindrical surface of said axial bore adjacent the other end of said valve element; an annular external groove in the outer cylindrical surface ofthe actuatable member normally in circular alignment with the circular teeth aforesaid; a split expansible ring engaging said external groove and having its external surface defined by complemental toothed elements cooperating with the toothed elements on the valve element to effect limited unison movement of the actuatable member and the valve element to its two operating positions of control, said cooperating teeth on the expansible ring and the valve element respectively being characterized by providing limited relative ratcheting engagement upon termination of the aforesaid limited unison movement to establish the valve element in its operating positions of control whereby such positionsof control are establshable at different operating positions other than normal position of said actuatable member within the limits of said relative ratcheting engagement thereof with said valve element; a split stop ring engaging an internal annular groove in said wall adjacent one end thereof to limit relative operating movement of said valve element to establish one of its operatingl positions; another split stop ring engaging another annular internal groove in said wall adjacent the other end thereof, and engageable by the other ends of said valve element and actuatable member respectively to establish their respective normal operating positions wherein the flange on the actuatable member is engaged by the confronting end of the valve element; a stationary member; a slidable member having a normal position; an element interconnecting said slid- Vable member with the valve element for conjoint movement; and a normally preloaded spring reacting between said stationary member and the slidable member to bias the latter member, said actuatable member and the valve element to their respective normal` positions wherein said other chamber is in communication with said second port.,

3. In control valve mechanism for use in cooperation with a fluid pressure actuated servomotor having a uid chamber enclosure and a movable wall dividing said chamber into opposing fluid pressure chambers, and a source of pressure different from atmosphere communicable with one of said pressure chambers, the improvement which comprises; a fixed member; a pair of interlitting valve elements cooperable in normal disposition to balance pressures in said chambers, and relatively displaceable to operating disposition to establish differential pressures-in said chambers; spring means including a normally preloaded spring reacting between said xed member and one of `said valve elements to establish them in their normal disposition; and an operatoroperated member having a normallyreleased position, and adapted to act on said one valve element to effect said relative displacement of said valve elements in Yopposition to said spring means, said means being characterized by progressively augmented reaction on said operator member in accordance with the operating movement thereof from normal position.

` 4. In control valve mechanism for use in cooperation with a iuid pressure actuated servomotor having a fluid chamber enclosure and a movable Wall dividing said chamber into opposing fluid pressure chambers, and a source of pressure different from atmosphere communicable with one of said pressure chambers, the improvement which comprises: a iXed member; a pair of intertting valve elements cooperable in normal disposition to balance pressures in said chambers, and relatively displaceable to operating position to establish differential pressures in said chambers; an actuatable member cooperating With one of said pair of valve elements; an operator-operated member having a normally released position, and adapted to actuate said actuatable member; means releasably interconnecting said actuatable member and said one valve element for movement together to eect said relative displacement of said valve elements, said means being operative upon full relative displacement of said valve elements to release said actuatable member from said one valve element without disturbing its then existent relatively displaced disposition thereof I in response to increased operator force on said operator member in a valve displacing direction thereby raccommodating relative movement of said operator member with respect to said valve elements, and to restore said valve elements to their normal disposition at substantially the operated position of the operator member upon release of the `latter member therefrom; and spring means including a normally preloaded spring reacting between said fixed member and said actuatable member to establish said valve elements, said actuatable and operator members in their normal disposition, said spring means being characterized by progressively augmented reaction on said operator member in accordance With the operating movement thereof from normal position.

References Cited in the le of this patent UNITED STATES PATENTS 

